U.S. law enforcement and intelligence officials are focusing on the possibility that at least one of the Malaysia Airlines pilots is responsible for the disappearance of flight MH 370 after new information revealed the plane performed "tactical evasion maneuvers" after it disappeared from radar, two senior law enforcement officials told ABC News today.

U.S. authorities believe only a person with extensive flight or engineering experience could have executed the maneuvers. They also are suspicious of what appeared to be attempts to evade radar.

After the plane's transponder -- which reports the plane's location and altitude -- was turned off about 1:20 a.m. last Saturday, the plane was picked up by military radar as it turned back towards Malaysia and passed above Peninsular Malaysia before heading into the Strait of Malacca.

ABC News

The search area for Malaysia Airlines Flight MH370 now includes two corridors: one stretching from approximately the border of Kazakhstan and Turkmenistan to northern Thailand and another stretching across Indonesia to the southern Indian Ocean.

The U.S. assessment squares with Malaysian Prime Minister Najib Razak statement today that "these movements are consistent with deliberate action by someone on the plane."

After a week of scrutinizing passengers and the crew, one of the officials said there were no indications anyone besides the pilots had the ability to perform the complicated maneuvers done by the plane. Furthermore, officials said they have found no link between the passengers and known terrorist groups and that the plane could have been flown into a densely populated area if the incident was related to terrorism -- but it wasn't.

Another possibility that can't be ruled out is that the pilots were coerced or made to redirect the plane by force.

ABC News aviation expert and former Marine Corps fighter pilot Steve Ganyard said it's possible that the movements made by the plane could mean it was piloted by amateurs not used to flying at night.

Ganyard said a person trying to fly a plane without lights or a horizon could make random turns that may appear to be evasive but were just accidental.

"[A hijacker could] tell the pilot 'turn the transponder off' and hold a gun to his head," Ganyard said. "They could advertently fly out to sea hoping to see some to land to go towards."

Ganyard also noted that the hijackers of United Flight 93 on Sept. 11 raised and lowered the altitude to try and stop the passengers who were storming the cockpit.

Earlier in the day, Malaysian police visited the home of Capt. Zaharie Ahmad Shah, the 53-year-old pilot of the missing plane.

Shah is a married father of three grown children with more than 18,000 hours of experience in the air. He has been described as an affluent aviation buff, with a home in a gated community that police spent about two hours inside today.

The first officer, Fariq Abdul Hamid, 27, joined Malaysia Airlines in 2007 and has 2,000 hours of flying time.

In recent days the Malaysian government has been criticized for not sharing information earlier with international investigators.

A senior Western law enforcement official told ABC News today that the Malaysian government repeatedly turned down assistance from Interpol to assist in its investigation. That offer has since been repeated several times and declined each time.

"It's the old pre-9/11 approach: close-hold information, don't share anything," the official said.

A spokeswoman for Interpol declined comment.

Law enforcement officials are now worried that critical investigative time has been lost and leads could well have dried up as sources of information could have dispersed in the last week. The FBI also hasn't been invited by the Malaysian government to help on the ground, sources said.

"Malaysia Airlines has shared all available information with the relevant authorities since the moment we learned that the aircraft had disappeared," read a statement from the airline. "This is truly an unprecedented situation, for Malaysia Airlines and for the entire aviation industry."

At a Saturday news conference Malaysian Prime Minister Najib Razak said that the plane was steered off course by someone on board, was airborne for more than seven hours and may have traveled as far as Kazakhstan. He added that although the movements were consistent with deliberate acts, he wouldn't confirm that the plane was hijacked.

"We are still investigating all possibilities as to what caused MH370 to deviate from its original flight path," he said.

Razak presented a vastly different timeline that what had officials had previously acknowledged -- saying for the first time that the last confirmed communication between the plane and a satellite was at 8:11 a.m. Malaysian time. The prime minister said the search has expanded to points as far north as Kazakhstan and as far south as the South Indian Ocean -- a stretch of more than 5,000 miles.

The flight was carrying 239 people when it disappeared while above waters between Malaysia and Vietnam. A frantic search followed, with 14 different countries involved.

The plane's communication systems were shut down separately, two U.S. officials said, an indication that the plane did not come out of the sky because of a catastrophic failure.

The data reporting system, they believe, was shut down at 1:07 a.m. The transponder – which transmits location and altitude – shut down at 1:21 a.m. The missing flight continued to "ping" a satellite on an hourly basis after it lost contact with radar, senior administration officials told ABC News.